Substrate and collector grid structures for integrated series connected photovoltaic arrays and process of manufacture of such arrays

ABSTRACT

This invention comprises deposition of thin film photovoltaic junctions on metal substrates which can be heat treated following deposition in a continuous fashion without deterioration of the metal support structure. In a separate operation an interconnection substrate structure is produced in a continuous roll-to-roll fashion. In this way the interconnection substrate structure can be uniquely formulated from polymer-based materials since it does not have to endure high temperature exposure. Cells comprising the metal foil supported photovoltaic junctions are then laminated to the interconnection substrate structure. Conductive interconnections are deposited to complete the array. The conductive interconnections can be accomplished with a separately prepared interconnection component. The interconnected array is produced using continuous roll-to-roll processing which avoids the need to use the expensive and intricate material removal operations currently taught in the art to achieve electrical interconnections among arrays of photovoltaic cells.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.10/682,093 filed Oct. 8, 2003, entitled Substrate and Collector GridStructures for Integrated Series Connected Photovoltaic Arrays andProcess of Manufacture of Such Arrays which is a Continuation-in-Part ofU.S. patent application Ser. No. 10/186,546 filed Jul. 1, 2002, entitledSubstrate and Collector Grid Structures for Integrated Series ConnectedPhotovoltaic Arrays and Process of Manufacture of Such Arrays, nowabandoned, which is a Continuation-in-Part of U.S. patent applicationSer. No. 09/528,086, filed Mar. 17, 2000, entitled Substrate andCollector Grid Structures for Integrated Series Connected PhotovoltaicArrays and Process of Manufacture of Such Arrays, and now U.S. Pat. No.6,414,235, which is a Continuation-in-Part of U.S. patent applicationSer. No. 09/281,656, filed Mar. 30, 1999, entitled Substrate andCollector Grid Structures for Electrically Interconnecting PhotovoltaicArrays and Process of Manufacture of Such Arrays, and now U.S. Pat. No.6,239,352. The entire contents of the above identified applications areincorporated herein by this reference.

BACKGROUND OF THE INVENTION

Photovoltaic cells have developed according to two distinct methods. Theinitial operational cells employed a matrix of single crystal siliconappropriately doped to produce a planar p-n junction. An intrinsicelectric field established at the p-n junction produces a voltage bydirecting solar photon produced holes and free electrons in oppositedirections. Despite good conversion efficiencies and long-termreliability, widespread energy collection using single-crystal siliconcells is thwarted by the exceptionally high cost of single crystalsilicon material and interconnection processing.

A second approach to produce photovoltaic cells is by depositing thinphotovoltaic semiconductor films on a supporting substrate. Materialrequirements are minimized and technologies can be proposed for massproduction. The thin film structures can be designed according to dopedhomojunction technology such as that involving silicon films, or canemploy heterojunction approaches such as those using CdTe orchalcopyrite materials. Despite significant improvements in individualcell conversion efficiencies for both single crystal and thin filmapproaches, photovoltaic energy collection has been generally restrictedto applications having low power requirements. One factor impedingdevelopment of bulk power systems is the problem of economicallycollecting the energy from an extensive collection surface. Photovoltaiccells can be described as high current, low voltage devices. Typicallyindividual cell voltage is less than one volt. The current component isa substantial characteristic of the power generated. Efficient energycollection from an expansive surface must minimize resistive lossesassociated with the high current characteristic. A way to minimizeresistive losses is to reduce the size of individual cells and connectthem in series. Thus, voltage is stepped through each cell while currentand associated resistive losses are minimized.

It is readily recognized that making effective, durable seriesconnections among multiple small cells can be laborious, difficult andexpensive. In order to approach economical mass production of seriesconnected arrays of individual cells, a number of factors must beconsidered in addition to the type of photovoltaic materials chosen.These include the substrate employed and the process envisioned. Sincethin films can be deposited over expansive areas, thin film technologiesoffer additional opportunities for mass production of interconnectedarrays compared to inherently small, discrete single crystal siliconcells. Thus a number of U.S. patents have issued proposing designs andprocesses to achieve series interconnections among the thin filmphotovoltaic cells. Many of these technologies comprise deposition ofphotovoltaic thin films on glass substrates followed by scribing to formsmaller area individual cells. Multiple steps then follow toelectrically connect the individual cells in series array. Examples ofthese proposed processes are presented in U.S. Pat. Nos. 4,443,651,4,724,011, and 4,769,086 to Swartz, Turner et al. and Tanner et al.respectively. While expanding the opportunities for mass production ofinterconnected cell arrays compared with single crystal siliconapproaches, glass substrates must inherently be processed on anindividual batch basis.

More recently, developers have explored depositing wide area films usingcontinuous roll-to-roll processing. This technology generally involvesdepositing thin films of photovoltaic material onto a continuouslymoving web. However, a challenge still remains regarding subdividing theexpansive films into individual cells followed by interconnecting into aseries connected array. For example, U.S. Pat. No. 4,965,655 to Grimmeret. al. and U.S. Pat. No. 4,697,041 to Okamiwa teach processes requiringexpensive laser scribing and interconnections achieved with laser heatstaking. In addition, these two references teach a substrate of thinvacuum deposited metal on films of relatively expensive polymers. Theelectrical resistance of thin vacuum metallized layers significantlylimits the active area of the individual interconnected cells.

It has become well known in the art that the efficiencies of certainpromising thin film photovoltaic junctions can be substantiallyincreased by high temperature treatments. These treatments involvetemperatures at which even the most heat resistant plastics suffer rapiddeterioration, thereby requiring either ceramic, glass, or metalsubstrates to support the thin film junctions. Use of a glass or ceramicsubstrates generally restricts one to batch processing and handlingdifficulty. Use of a metal foil as a substrate allows continuousroll-to-roll processing. However, despite the fact that use of a metalfoil allows high temperature processing in roll-to-roll fashion, thesubsequent interconnection of individual cells effectively in aninterconnected array has proven difficult, in part because the metalfoil substrate is electrically conducting.

U.S. Pat. No. 4,746,618 to Nath et al. teaches a design and process toachieve interconnected arrays using roll-to-roll processing of a metalweb substrate such as stainless steel. The process includes multipleoperations of cutting, selective deposition, and riveting. Theseoperations add considerably to the final interconnected array cost.

U.S. Pat. No. 5,385,848 to Grimmer teaches roll-to-roll methods toachieve integrated series connections of adjacent thin film photovoltaiccells supported on an electrically conductive metal substrate. Theprocess includes mechanical or chemical etch removal of a portion of thephotovoltaic semiconductor and transparent top electrode to expose aportion of the electrically conductive metal substrate. The exposedmetal serves as a contact area for interconnecting adjacent cells. Thesematerial removal techniques are troublesome for a number of reasons.First, many of the chemical elements involved in the best photovoltaicsemiconductors are expensive and environmentally unfriendly. Thisremoval subsequent to controlled deposition involves containment, dustand dirt collection and disposal, and possible cell contamination. Thisis not only wasteful but considerably adds to expense. Secondly, theremoval processes are difficult to control dimensionally. Thus asignificant amount of the valuable photovoltaic semiconductor is lost tothe removal process. Ultimate module efficiencies are furthercompromised in that the spacing between adjacent cells grows, therebyreducing the effective active collector area for a given module area.

Thus there remains a need for an inexpensive manufacturing process whichallows high heat treatment for thin film photovoltaic junctions whilealso offering unique means to achieve effective integrated seriesconnections.

A further unsolved problem which has thwarted production of expansivesurface photovoltaic modules is that of collecting the photogeneratedcurrent from the top, light incident surface. Transparent conductiveoxide (TCO) layers have been employed as a top surface electrode.However, these TCO layers are relatively resistive compared to puremetals. This fact forces individual cell widths to be reduced in orderto prevent unacceptable resistive power losses. As cell widths decrease,the width of the area between individual cells (interconnect area)should also decrease so that the relative portion of inactive surface ofthe interconnect area does not become excessive. Typical cell widths ofone centimeter are often taught in the art. These small cell widthsdemand very fine interconnect area widths, which dictate delicate andsensitive techniques to be used to electrically connect the top TCOsurface of one cell to the bottom electrode of an adjacent seriesconnected cell. Furthermore, achieving good stable ohmic contact to theTCO cell surface has proven difficult, especially when one employs thosesensitive techniques available when using the TCO only as the topcollector electrode. The problem of collecting photovoltaic generatedcurrent from the top-light impinging surface of a photovoltaic cell hasbeen addressed in a number of ways, none entirely successful.

In a somewhat removed segment of technology, a number of electricallyconductive fillers have been used to produce electrically conductivepolymeric materials. This technology generally involves mixing of theconductive filler into the polymer resin prior to fabrication of thematerial into its final shape. Conductive fillers typically consist ofhigh aspect ratio particles such as metal fibers, metal flakes, orhighly structured carbon blacks, with the choice based on a number ofcost/performance considerations. Electrically conductive resins havebeen used as bulk thermoplastic compositions, or formulated into paints.Their development has been spurred in large part by electromagneticradiation shielding and static discharge requirements for plasticcomponents used in the electronics industry. Other known applicationsinclude resistive heating fibers and battery components.

In yet another separate technological segment, electroplating on plasticsubstrates has been employed to achieve decorative effects on items suchas knobs, cosmetic closures, faucets, and automotive trim. ABS(acrylonitrile-butadiene-styrene) plastic dominates as the substrate ofchoice for most applications because of a blend of mechanical andprocess properties and ability to be uniformly etched. The overallplating process comprises many steps. First, the plastic substrate ischemically etched to microscopically roughen the surface. This isfollowed by depositing an initial metal layer by chemical reduction(typically referred to as “electroless plating”). This initial metallayer is normally copper or nickel of thickness typically one-halfmicrometer. The object is then electroplated with metals such as brightnickel and chromium to achieve the desired thickness and decorativeeffects. The process is very sensitive to processing variables used tofabricate the plastic substrate, limiting applications to carefullymolded parts and designs. In addition, the many steps employing harshchemicals make the process intrinsically costly and environmentallydifficult. Finally, the sensitivity of ABS plastic to liquidhydrocarbons has prevented certain applications. The conventionaltechnology for electroplating on plastic (etching, chemical reduction,electroplating) has been extensively documented and discussed in thepublic and commercial literature. See, for example, Saubestre,Transactions of the Institute of Metal Finishing, 1969, Vol. 47, orArcilesi et al., Products Finishing, March 1984.

Many attempts have been made to simplify the process of electroplatingon plastic substrates. Some involve special chemical techniques toproduce an electrically conductive film on the surface. Typical examplesof this approach are taught by U.S. Pat. No. 3,523,875 to Minklei, U.S.Pat. No. 3,682,786 to Brown et. al., and U.S. Pat. No. 3,619,382 toLupinski. The electrically conductive film produced was thenelectroplated. None of these attempts at simplification have achievedany recognizable commercial application.

A number of proposals have been made to make the plastic itselfconductive enough to allow it to be electroplated directly therebyavoiding the “electroless plating” process. Efforts to advance systemscontemplating metal electrodeposition directly onto the surface of anelectrically conductive polymer have encountered a number of obstacles.The first is the combination of fabrication difficulty and materialproperty deterioration brought about by the heavy filler loadings oftenrequired. A second is the high cost of many conductive fillers employedsuch as silver flake.

Another major obstacle involved in the electroplating of electricallyconductive polymers is a consideration of adhesion between theelectrodeposited metal and polymeric substrate (metal/polymer adhesion).In some cases such as electroforming, where the electrodeposited metalis eventually removed from the substrate, metal/polymer adhesion mayactually be detrimental. However, in most cases sufficient adhesion isrequired to prevent metal/polymer separation during extendedenvironmental and use cycles.

A number of methods to enhance adhesion have been employed. For example,etching of the surface prior to plating can be considered. Etching canbe achieved by immersion in vigorous solutions such as chromic/sulfuricacid. Alternatively, or in addition, an etchable species can beincorporated into the conductive polymeric compound. The etchablespecies at exposed surfaces is removed by immersion in an etchant priorto electroplating. Oxidizing surface treatments can also be consideredto improve metal/plastic adhesion. These include processes such as flameor plasma treatments or immersion in oxidizing acids.

In the case of conductive polymers containing finely divided metal, onecan propose achieving direct metal-to-metal adhesion betweenelectrodeposit and filler. However, here the metal particles aregenerally encapsulated by the resin binder, often resulting in a resinrich “skin”. To overcome this effect, one could propose methods toremove the “skin”, exposing active metal filler to bond to subsequentlyelectrodeposited metal.

Another approach to impart adhesion between conductive resin substratesand electrodeposits is incorporation of an “adhesion promoter” at thesurface of the electrically conductive resin substrate. This approachwas taught by Chien et al. in U.S. Pat. No. 4,278,510 where maleicanhydride modified propylene polymers were taught as an adhesionpromoter. Luch, in U.S. Pat. No. 3,865,699 taught that certain sulfurbearing chemicals could function to improve adhesion of initiallyelectrodeposited Group VIII metals.

An additional major obstacle confronting development of electricallyconductive polymeric resin compositions capable of being directlyelectroplated is the initial “bridge” of electrodeposit on the surfaceof the electrically conductive resin. In electrodeposition, thesubstrate to be plated is normally made cathodic through a pressurecontact to a metal rack tip, itself under cathodic potential. However,if the contact resistance is excessive or the substrate isinsufficiently conductive, the electrodeposit current favors the racktip to the point where the electrodeposit will not bridge to thesubstrate.

Moreover, a further problem is encountered even if specialized rackingsuccessfully achieves electrodeposit bridging to the substrate. Many ofthe electrically conductive polymeric resins have resistivities farhigher than those of typical metal substrates. The polymeric substratecan be relatively limited in the amount of electrodeposition currentwhich it alone can convey. Thus, the conductive polymeric substrate doesnot cover almost instantly with electrodeposit as is typical withmetallic substrates. Except for the most heavily loaded and highlyconductive polymer substrates, a large portion of the electrodepositioncurrent must pass back through the previously electrodeposited metalgrowing laterally over the surface of the conductive plastic substrate.In a fashion similar to the bridging problem discussed above, theelectrodeposition current favors the electrodeposited metal and thelateral growth can be extremely slow and erratic. This restricts thesize and “growth length” of the substrate conductive pattern, increasesplating costs, and can also result in large non-uniformities inelectrodeposit integrity and thickness over the pattern.

This lateral growth is dependent on the ability of the substrate toconvey current. Thus, the thickness and resistivity of the conductivepolymeric substrate can be defining factors in the ability to achievesatisfactory electrodeposit coverage rates. When dealing withselectively electroplated patterns long thin metal traces are oftendesired, deposited on a relatively thin electrically conductive polymersubstrate. These factors of course work against achieving the desiredresult.

This coverage rate problem likely can be characterized by a continuum,being dependent on many factors such as the nature of the initiallyelectrodeposited metal, electroplating bath chemistry, the nature of thepolymeric binder and the resistivity of the electrically conductivepolymeric substrate. As a “rule of thumb”, the instant inventorestimates that coverage rate problems would demand attention if theresistivity of the conductive polymeric substrate rose above about 0.001ohm-cm.

Beset with the problems of achieving adhesion and satisfactoryelectrodeposit coverage rates, investigators have attempted to producedirectly electroplateable polymers by heavily loading polymers withrelatively small metal containing fillers. Such heavy loadings aresufficient to reduce both microscopic and macroscopic resistivity to alevel where the coverage rate phenomenon may be manageable. However,attempts to make an acceptable directly electroplateable resin using therelatively small metal containing fillers alone encounter a number ofbarriers. First, the fine metal containing fillers are relativelyexpensive. The loadings required to achieve the particle-to-particleproximity to achieve acceptable conductivity increases the cost of thepolymer/filler blend dramatically. The metal containing fillers areaccompanied by further problems. They tend to cause deterioration of themechanical properties and processing characteristics of many resins.This significantly limits options in resin selection. All polymerprocessing is best achieved by formulating resins with processingcharacteristics specifically tailored to the specific process (injectionmolding, extrusion, blow molding etc.). A required heavy loading ofmetal filler severely restricts ability to manipulate processingproperties in this way. A further problem is that metal fillers can beabrasive to processing machinery and may require specialized screws,barrels, and the like. Finally, despite being electrically conductive, asimple metal-filled polymer still offers no mechanism to produceadhesion of an electrodeposit since the metal particles are generallyencapsulated by the resin binder, often resulting in a non-conductiveresin-rich “skin”. For the above reasons, fine metal particle containingplastics have not been widely used as substrates for directlyelectroplateable articles. Rather, they have found applications inproduction of conductive adhesives, pastes, and paints.

The least expensive (and least conductive) of the readily availableconductive fillers for plastics are carbon blacks. Attempts have beenmade to produce electrically conductive polymers based on carbon blackloading intended to be subsequently electroplated. Examples of thisapproach are the teachings of U.S. Pat. Nos. 4,038,042, 3,865,699, and4,278,510 to Adelman, Luch, and Chien et al. respectively.

Adelman taught incorporation of conductive carbon black into a polymericmatrix to achieve electrical conductivity required for electroplating.The substrate was pre-etched in chromic/sulfuric acid to achieveadhesion of the subsequently electroplated metal. A fundamental problemremaining unresolved by the Adelman teaching is the relatively highresistivity of carbon loaded polymers. The lowest “microscopicresistivity” generally achievable with carbon black loaded polymers isabout 1 ohm-cm. This is about five to six orders of magnitude higherthan typical electrodeposited metals such as copper or nickel. Thus, theelectrodeposit bridging and coverage rate problems described aboveremained unresolved by the Adelman teachings.

Luch in U.S. Pat. No. 3,865,699 and Chien et al. in U.S. Pat. No.4,278,510 also chose carbon black as an electrically conductive fillerfor polymeric compounds to be electroplated. However, these inventorsfurther taught incorporation of an electrodeposit coverage or depositionrate accelerator to overcome the galvanic bridging and lateralelectrodeposit growth rate problems described above. In the embodiments,examples and teachings of U.S. Pat. Nos. 3,865,699 and 4,278,510, it wasshown that certain sulfur bearing materials, including elemental sulfur,can function as electrodeposit coverage or growth rate accelerators toovercome those problems associated with electrically conductivepolymeric substrates having relatively high resistivity. In addition toelemental sulfur, sulfur in the form of sulfur donors such as sulfurchloride, 2-mercapto-benzothiazole, N-cyclohexyle-2-benzothiaozolesulfonomide, dibutyl xanthogen disulfide, and tetramethyl thiuramdisulfide or combinations of these and sulfur were identified. Thoseskilled in the art will recognize that these sulfur donors are thematerials which have been used or have been proposed for use asvulcanizing agents or accelerators. Since the polymer-based compositionstaught by Luch and Chien et al. could be electroplated directly theycould be accurately defined as directly electroplateable resins (DER).These resins can be generally described as electrically conductivepolymers with the inclusion of a growth rate accelerator.

Specifically for the present invention, specification, and claims,directly electroplateable resins, (DER), are characterized by thefollowing features.

(a) having a polymer or resin matrix or binder;

(b) presence of conductive fillers in the polymer matrix in amountssufficient to provide an electrical volume resistivity of thepolymer/conductive filler mix, which is sufficiently low to allow directelectrodeposition. Typically, a resistivity less than 1000 ohm-cm.,e.g., 100 ohm-cm., 10 ohm-cm., 1 ohm-cm. 0.1 ohm-cm., 0.01 ohm-cm.,0.001 ohm-cm., suffices;

(c) presence of an electrodeposit coverage rate accelerator;

(d) presence of the polymer, conductive filler and electrodepositcoverage rate accelerator in the directly electroplateable compositionin cooperative amounts required to achieve direct coverage of thecomposition with an electrodeposited metal or metal-based alloy. It hasbeen found that Group VIII metals or Group VIII metal-based alloys areparticularly suitable as the initial electrodeposit on the DER surface.

It is understood the electrical conductivity required to allow fordirect electrodeposition can also be achieved thru the use of aninherently conductive polymer. In this instance it may not be necessaryto add electrical fillers to the polymer.

In his patents, Luch specifically identified unsaturated elastomers suchas natural rubber, polychloroprene, butyl rubber, chlorinated butylrubber, polybutadiene rubber, acrylonitrile-butadiene rubber,styrene-butadiene rubber etc. as suitable for the matrix polymer of adirectly electroplateable resin. Other polymers identified by Luch asuseful included polyvinyls, polyolefins, polystyrenes, polyamides,polyesters and polyurethanes.

When used alone, the minimum workable level of carbon black required toachieve “microscopic” electrical resistivities of less than 1000 ohm-cm.for a polymer/carbon black mix appears to be about 8 weight percentbased on the combined weight of polymer plus carbon black. The“microscopic” material resistivity generally is not reduced below about1 ohm-cm. by using conductive carbon black alone. This is several ordersof magnitude larger than typical metal resistivities. Other well known,finely divided highly conductive fillers (such as metal flake) can beconsidered in DER applications requiring lower “microscopic”resistivity. In these cases the more highly conductive fillers can beused to augment or even replace the conductive carbon black.

The “bulk, macroscopic” resistivity of conductive carbon black filledpolymers can be further reduced by augmenting the carbon black fillerwith additional highly conductive, high aspect ratio fillers such asmetal containing fibers. This can be an important consideration in thesuccess of certain applications. Furthermore, one should realize thatincorporation of non-conductive fillers may increase the “bulk,macroscopic” resistivity of conductive polymers loaded with finelydivided conductive fillers without significantly altering the“microscopic resistivity” of the conductive polymer “matrix”encapsulating the non-conductive filler particles.

It is important to recognize a number of important characteristics ofdirectly electroplateable resins (DERs) which facilitate the currentinvention. First, regarding electrodeposit coverage rate accelerators,both Luch and Chien et al. in the above discussed U.S. patentsdemonstrated that sulfur and other sulfur bearing materials such assulfur donors and accelerators served this purpose when using an initialGroup VIII “strike” layer. One might expect that other elements of Group6A nonmetals, such as oxygen, selenium and tellurium, could function ina way similar to sulfur. In addition, other combinations ofelectrodeposited metals and nonmetal coverage rate accelerators may beidentified. It is important to recognize that such an electrodepositcoverage accelerator is extremely important in order to achieve directelectrodeposition in a practical way onto polymeric substrates havingrelatively high resistivity compared to metals (i.e. 0.001 ohm-cm. orabove) or very thin electrically conductive polymeric substrates havingrestricted current carrying ability.

A second important characteristic of directly electroplateable resins isthat electrodeposit coverage speed depends not only on the presence ofan electrodeposit coverage rate accelerator but also on the “microscopicresistivity” and less so on the “macroscopic resistivity” of the DERformulation. Thus, large additional loadings of functionalnon-conductive fillers can be tolerated in DER formulations withoutundue sacrifice in electrodeposit coverage or adhesion. These additionalnon-conductive loadings do not greatly affect the “microscopicresistivity” associated with the polymer/conductivefiller/electrodeposit coverage accelerator “matrix” since thenon-conductive filler is essentially encapsulated by “matrix” material.Conventional “electroless” plating technology does not permit thiscompositional flexibility.

A third important characteristic of DER technology is its ability toemploy polymer resins generally chosen in recognition of the fabricationprocess envisioned and the intended end use requirements. For example,should an extrusion blow molding fabrication be desired, resins havingthe required high melt strength can be employed. Should the part beinjection molded and have thin wall cross-sections, a typical situationencountered in selective design of conductive trace patterns, a highflow resin can be chosen. Should a coating, ink, paint, or paste beenvisioned, a soluble resin such as an elastomer can be considered. Allpolymer fabrication processes require specific resin processingcharacteristics for success. The ability to “custom formulate” DER's tocomply with these changing processing and end use requirements whilestill allowing facile, quality electroplating is a significant factor inthe electroplating teachings of the current invention. Conventional“electroless” plating technology does not permit great flexibility to“custom formulate”.

Due to multiple performance problems associated with their intended-enduse, none of the attempts identified above to directly electroplateelectrically conductive polymers or plastics has ever achieved anyrecognizable commercial success. Nevertheless, the current inventor haspersisted in personal efforts to overcome certain performancedeficiencies associated with the initial DER technology. Along withthese efforts has come a recognition of unique and eminently suitableapplications employing the DER technology. Some examples of these uniqueapplications for electroplated articles include solar cell electricalcurrent collection grids, electrical circuits, electrical traces,circuit boards, antennas, capacitors, induction heaters, connectors,switches, resistors, inductors, batteries, fuel cells, coils, signallines, power lines, radiation reflectors, coolers, diodes, transistors,piezoelectric elements, photovoltaic cells, emi shields, biosensors andsensors. One readily recognizes that the demand for such functionalapplications for electroplated articles is relatively recent and hasbeen particularly explosive during the past decade.

While not precisely definable, electrically insulating materials maygenerally be characterized as having electrical resistivities greaterthan 10,000 ohm-cm. Also, electrically conductive materials maygenerally be characterized as having electrical resistivities less than0.001 ohm-cm. Also electrically resistive or semi-conductive materialsmay generally be characterized as having electrical resistivities in therange of 0.001 ohm-cm to 10,000 ohm-cm. The characterization“electrically conductive polymer” covers a very wide range of intrinsicresistivities depending on the filler, the filler loading and themethods of manufacture of the filler/polymer blend. Resistivities forelectrically conductive polymers may be as low as 0.00001 ohm-cm. forvery heavily filled silver inks, yet may be as high as 10,000 ohm-cm oreven more for lightly filled carbon black materials or other“anti-static” materials. “Electrically conductive polymer” has become abroad industry term to characterize all such materials. Thus, the term“electrically conductive polymer” as used in the art and in thisspecification and claims extends to materials of a very wide range ofresitivities from about 0.00001 ohm-cm. to about 10,000 ohm-cm andhigher.

In order to eliminate ambiguity in terminology, for the presentinvention the following definitions are supplied:

“Metal-based” refers to a material or structure having at least onemetallic property and comprising one or more components at least one ofwhich is a metal or metal-containing alloy.

“Alloy” refers to a substance composed of two or more intimately mixedmaterials.

“Group VIII metal-based” refers to a substance containing by weight 50%to 100% metal from Group VIII of the Periodic Table of Elements.

OBJECTS OF THE INVENTION

An object of the invention is to eliminate the deficiencies in the priorart methods of producing expansive area, series interconnectedphotovoltaic arrays. A further object of the present invention is toprovide improved substrates to achieve series interconnections amongexpansive thin film cells.

A further object of the invention is to permit inexpensive production ofhigh efficiency, heat treated thin film photovoltaic cells whilesimultaneously permitting the use of polymer based substrate materialsand associated processing to effectively interconnect those cells.

A further object of the present invention is to provide improvedprocesses whereby expansive area, series interconnected photovoltaicarrays can be economically mass produced.

A further object of the invention is to provide improved processes andstructures for supplying current collector grids.

Other objects and advantages will become apparent in light of thefollowing description taken in conjunction with the drawings andembodiments.

SUMMARY OF THE INVENTION

The current invention provides a solution to the stated need byproducing the active photovoltaic film and interconnecting substrateseparately and subsequently combining them to produce the desiredexpansive series interconnected array. The invention contemplatesdeposition of thin film photovoltaic junctions on metal foil substrateswhich can be heat treated following deposition in a continuous fashionwithout deterioration of the metal support structure. In a separateoperation, an interconnection substrate structure is produced in acontinuous roll-to-roll fashion.

The metal foil supported photovoltaic junction is then laminated to theinterconnecting substrate structure and conductive connections aredeposited to complete the array. In this way the interconnectionsubstrate structure can be uniquely formulated from polymer-basedmaterials since it does not have to endure high temperature exposure.Furthermore, the photovoltaic junction and its metal foil support can beproduced in bulk without the need to use the expensive and intricatematerial removal operations currently taught in the art to achieveseries interconnections.

BRIEF DESCRIPTION OF THE DRAWINGS

The various factors and details of the structures and manufacturingmethods of the present invention are hereinafter more fully set forthwith reference to the accompanying drawings wherein:

FIG. 1 is a top plan view of a thin film photovoltaic cell including itssupport foil.

FIG. 2 is a sectional view taken substantially along the line 2-2 ofFIG. 1.

FIG. 3 is an expanded sectional view showing a form of the structure oflayer II of FIG. 2.

FIG. 4 illustrates a process for producing the structure shown in FIGS.1-3.

FIG. 5 is a sectional view illustrating the problems associated withmaking series connections among thin film photovoltaic cells shown inFIGS. 1-3.

FIG. 6 is a top plan view of a substrate structure for achieving seriesinterconnections of thin film photovoltaic cells.

FIG. 7 is a sectional view taken substantially along the line 7-7 ofFIG. 6.

FIG. 8 is a sectional view similar to FIG. 7 showing an alternateembodiment of a substrate structure for achieving seriesinterconnections of thin film photovoltaic cells.

FIG. 9 is a top plan view of an alternate embodiment of a substratestructure for achieving series interconnections of thin filmphotovoltaic cells.

FIG. 10 is a sectional view similar to FIGS. 7 and 8 taken substantiallyalong line 10-10 of FIG. 9.

FIG. 11 is a top plan view of another embodiment of a substratestructure for achieving series interconnections of thin filmphotovoltaic cells.

FIG. 12 is a sectional view taken substantially along the line 12-12 ofFIG. 11.

FIGS. 13A and 13B schematically depict a process for laminating the foilsupported thin film photovoltaic structure of FIGS. 1 through 3 to aninterconnecting substrate structure. FIG. 13A is a side view of theprocess. FIG. 13B is a sectional view taken substantially along line13B-13B of FIG. 13A.

FIGS. 14A, 14B, and 14C are views of the structures resulting from thelaminating process of FIG. 13 and using the substrate structure of FIGS.7, 8, and 10 respectively.

FIGS. 15A, 15B, and 15C are sectional views taken substantially alongthe lines 15 a-15 a, 15 b-15 b, and 15 c-15 c of FIGS. 14A, 14B, and 14Crespectively.

FIG. 16 is a top plan view of the structure resulting from thelaminating process of FIG. 13 and using the substrate structure of FIGS.11 and 12.

FIG. 17 is a sectional view taken substantially along the line 17-17 ofFIG. 16.

FIG. 18 is a top plan view of the structures of FIGS. 14A and 15A butfollowing an additional step in manufacture of the interconnected cells.

FIG. 19 is a sectional view taken substantially along the line 19-19 ofFIG. 18.

FIG. 20 is a top plan view of a completed interconnected array.

FIG. 21 is a sectional view taken substantially along line 21-21 of FIG.20.

FIG. 22 is a sectional view similar to FIG. 15A but showing an alternatemethod of accomplishing the mechanical and electrical joining of thelamination process of FIG. 13.

FIG. 23 is a sectional view similar to FIG. 15A but showing an alternateembodiment of the laminated structure.

FIG. 24 is a sectional view of an alternate embodiment.

FIG. 25 is a sectional view of the embodiment of FIG. 24 after a furtherprocessing step.

FIG. 26 is a sectional view of another embodiment of a laminatedintermediate article in the manufacture of series interconnected arrays.

FIG. 27 is a top plan view of a starting material for another embodimentof substrate structure.

FIG. 28 is a greatly magnified plan view of the material of FIG. 27.

FIG. 29 is a sectional view taken substantially along line 29-29 of FIG.28.

FIG. 30 is a sectional view taken substantially along line 30-30 of FIG.28.

FIG. 31 is a simplified sectional view representing the structuredepicted in FIGS. 29 and 30.

FIG. 32 is a view similar to FIG. 27 but defining three distinct areaportions of the structure produced by a process step.

FIG. 33 is a greatly magnified plan view of that portion of FIG. 32defined by “W2”.

FIG. 34 is a greatly magnified sectional view of a portion of thestructure of FIG. 33 taken substantially from the perspective of line34-34 of FIG. 33.

FIG. 35 is a sectional view similar to FIG. 34 showing the structurefollowing an optional additional process step.

FIG. 36 is a simplified plan view of the structure of FIG. 32 useful inillustrating the process and structure of the embodiment.

FIG. 37A is a simplified sectional view taken substantially along line37-37 of FIG. 36, useful in illustrating the process and structure ofthe embodiment.

FIG. 37B is a simplified sectional view similar to FIG. 37Aincorporating an optional additional process step.

FIG. 38 is a schematic depiction of a process for joining the foilsupported thin film photovoltaic structure of FIGS. 1 through 3 to thesubstrate structure of FIG. 32 or 36.

FIG. 39 illustrates one form of the process depicted in FIG. 38.

FIG. 40 is a view of the process of FIG. 39 taken substantially alongline 40-40 of FIG. 39.

FIG. 41 is a plan view of the structure resulting from the process ofFIG. 38.

FIG. 42A is an embodiment of the structure of FIG. 41 takensubstantially along line 42-42 of FIG. 41.

FIGS. 42B and 42C are views similar to 42A showing alternate embodimentsof the structure depicted in FIG. 41.

FIG. 43 is an enlarged view of the portion of FIG. 42A shown withincircle

FIG. 44 is a plan view of the structure of FIG. 43 after an additionalprocessing step.

FIG. 44A is a sectional view taken substantially along the line 44A-44Aof FIG. 44.

FIG. 45 is a view similar to FIG. 44 after a further processing step.

FIG. 46 is a top plan view of another embodiment of the novel substratestructures useful in the manufacture of series interconnectedphotovoltaic arrays.

FIG. 47 is a sectional view taken substantially along line 47-47 of FIG.46.

FIG. 48 is a view similar to FIG. 47 following an additional processingstep.

FIG. 49 is a sectional view similar to FIG. 43 illustrating an alternateprocessing sequence.

FIG. 50 is a top plan view of a starting component of an additionalembodiment of the invention.

FIG. 51 is a sectional view taken along line 51-51 of FIG. 50.

FIG. 52 is a simplified representation of the sectional view of FIG. 51.

FIG. 53 is a top plan view of the embodiment of FIGS. 50 through 52following an additional processing step.

FIG. 54 is a sectional view taken along the line 54-54 of FIG. 53.

FIG. 55 is a sectional view taken along the line 55-55 of FIG. 53.

FIG. 56 is a top plan view of embodiment of FIGS. 53 through 55 after anadditional processing step.

FIG. 57 is a sectional view taken along line 57-57 of FIG. 56.

FIG. 58 is a sectional view taken along line 58-58 of FIG. 56.

FIG. 59 is a sectional view taken along line 59-59 of FIG. 56.

FIG. 60 is a simplified representation of a process used in themanufacture of an embodiment of the invention.

FIG. 61 is a sectional view taken along the line 61-61 of FIG. 60 usingthe structures of FIGS. 19 and 59.

FIG. 62 is a sectional view showing a lamination resulting from theprocess of FIG. 60.

FIG. 63 is an enlarged sectional view of the portion of FIG. 62 withinCircle “A” of FIG. 62.

FIG. 64 is a simplified sectional view of a starting substrate componentfor an additional embodiment of the invention.

FIG. 65 is a sectional view of the FIG. 64 components followingadditional processing steps.

FIG. 66 is a sectional view of the structure resulting from combiningthe structures shown in FIGS. 56 and 65 using the process illustrated inFIG. 60.

FIG. 67 is a top plan view of a starting component for an additionalembodiment of the invention.

FIG. 68 is a sectional view taken along line 68-68 of FIG. 67.

FIG. 69 is a top plan view after an additional processing step employingthe structure of FIGS. 67 and 68.

FIG. 70 is a simplified sectional view taken along line 70-70 of FIG.69.

FIG. 71 is a top plan view, similar to FIG. 69, of an alternateembodiment.

FIG. 72 is a sectional view of the structure of FIG. 70 after anadditional processing step.

FIG. 73 is a sectional view of a portion of the FIG. 72 structure afteran additional processing step.

FIG. 74 is a sectional view similar to FIG. 13B just prior to theprocess illustrated in FIG. 13A, employing the structures shown in thesectional view in FIGS. 7 and 73.

FIG. 75 is a sectional view showing the structure resulting fromapplication of the process of FIG. 13A to the structural arrangementshown in FIG. 74.

FIG. 76 is a sectional view of the spacial positioning of the structureshown in FIG. 75 and an additional component of the embodiment justprior to a process employed to combine them.

FIG. 77 is a plan view taken along the line 77-77 of FIG. 76.

FIG. 78 is an alternate embodiment of the FIG. 77 structure.

FIG. 79 is yet another alternate embodiment of the FIG. 77 structure.

FIG. 80 is a sectional view showing one possible example of thestructural makeup of a portion the components illustrated in FIGS. 77through 79.

FIG. 81 is a sectional view of the structure resulting from the processenvisioned in FIG. 76.

FIG. 82 is an illustration of a lamination process used to produce anadditional embodiment of the series interconnected photovoltaic cells ofthe disclosure.

FIG. 83 embodies the results of the lamination process of FIG. 82.

DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals designate identicalor corresponding parts throughout several views and an additional letterdesignation is characteristic of a particular embodiment.

Referring to FIGS. 1 and 2, a thin film photovoltaic cell is generallyindicated by numeral 10. Cell 10 has a light-incident top surface 59 anda bottom surface 66. Structure 10 has a width X-10 and length Y-10.Width X-10 defines a first photovoltaic cell terminal edge 45 and secondphotovoltaic cell terminal edge 46. It is contemplated that length Y-10is considerably greater than width X-10 and length Y-10 can generally bedescribed as “continuous” or being able to be processed in aroll-to-roll fashion. FIG. 2 shows that cell 10 comprises a thin filmsemiconductor structure 11 supported by metal-based foil 12. Foil 12 hasfirst surface 65, second surface 66, and thickness “Z”. Metal-based foil12 may be of uniform composition or may comprise a laminate of two ormore metal-based layers. For example, foil 12 may comprise a base layerof inexpensive and processable metal 13 with an additional metal-basedlayer 14 disposed between base layer 13 and semiconductor structure 11.The additional metal-based layer may be chosen to ensure good ohmiccontact between the top surface 65 of support 12 and photovoltaicsemiconductor structure 11. Bottom surface 66 of foil support 12 maycomprise a material 75 chosen to achieve good electrical and mechanicaljoining characteristics to the substrate as will be shown. The thicknessZ of support layer 12 is generally contemplated to be between 0.001 cm.and 0.025 cm. This thickness would provide adequate handling strengthwhile still allowing flexibility for roll-to-roll processing.

Semiconductor structure 11 can be any of the thin film structures knownin the art. In its simplest form, a photovoltaic cell combines an n-typesemiconductor with a p-type semiconductor to from an n-p junction. Mostoften an optically transparent window electrode such as a thin film ofzinc or tin oxide is employed to minimize resistive losses involved incurrent collection. FIG. 3 illustrates an example of a typicalphotovoltaic cell structure in section. In FIGS. 2 and 3 and otherfigures, an arrow labeled “hv” is used to indicate the light incidentside of the structure. In FIG. 3, 15 represents a thin film of a p-typesemiconductor, 16 a thin film of n-type semiconductor and 17 theresulting photovoltaic junction. Window electrode 18 completes thetypical photovoltaic structure. The exact nature of the photovoltaicsemiconductor structure 11 does not form the subject matter of thepresent invention.

FIG. 4 refers to the method of manufacture of the foil supportedphotovoltaic structures generally illustrated in FIGS. 1 through 3. Themetal-based support foil 12 is moved in the direction of its length Ythrough a deposition process, generally indicated as 19. Process 19accomplishes deposition of the active photovoltaic structure ontosupport foil 12. Support foil 12 is unwound from supply roll 20 a,passed through deposition process 19 and rewound onto takeup roll 20 b.Process 19 can comprise any of the processes well-known in the art fordepositing thin film photovoltaic structures. These processes includeelectroplating, vacuum sputtering, and chemical deposition. Process 19may also include treatments, such as heat treatments, intended toenhance photovoltaic cell performance.

Referring now to FIG. 5, there are illustrated cells 10 as shown in FIG.2. The cells have been positioned to achieve spacial positioning on thesupport substrate 21. Support structure 21 is by necessitynon-conductive at least in that distance indicated by numeral 70separating the adjacent cells 10. This insulating space prevents shortcircuiting from metal foil electrode 12 of one cell to foil electrode 12of an adjacent cell. In order to achieve series connection, electricalcommunication must be made from the top surface of window electrode 18to the foil electrode 12 of an adjacent cell. This communication isshown in the FIG. 5 as a metal wire 41. Metal wire 41 is clearlyimpractical for inexpensive continuous production and is shown forillustration purposes only. The direction of the net current flow forthe arrangement shown in FIG. 5 is indicated by the double pointed arrow“I”.

It should be noted that foil electrode 12 is relatively thin, on theorder of 0.001 cm to 0.025 cm. Therefore connecting to its edge asindicated in FIG. 5 would be impractical. Referring now to FIGS. 6 and7, one embodiment of the interconnection substrate structures of thecurrent invention is generally indicated by 22. Unit of substrate 22comprises electrically conductive sheet region 23 and electricallyinsulating joining portion region 25. Electrically conductive sheetregion 23 has a top surface 26, bottom surface 28, width X-23, lengthY-23 and thickness Z-23. Width X-23 defines a first terminal edge 29 anda second terminal edge 30 of conductive sheet 23. Top surface 26 ofconductive sheet 23 can be thought of as having top collector surface 47and top contact surface 48 separated by imaginary insulating boundary49. The purpose for these definitions will become clear in thefollowing.

Electrically conductive sheet 23 includes an electrically conductivepolymer. Typically, electrically conductive polymers exhibit bulkresistivity values of less than 1000 ohm-cm. Resistivities less than1000 ohm-cm can be readily achieved by compounding well-known conductivefillers into a polymer matrix binder.

The substrate unit 22 may be fabricated in a number of different ways.Electrically conductive sheet 23 can comprise an extruded film ofelectrically conductive polymer joined to a strip of compatibleinsulating polymer 25 at or near terminal edge 29 as illustrated in FIG.7. Alternatively, the conductive sheet may comprise a strip ofelectrically conductive polymer 23 a laminated to an insulating supportstructure 31 as illustrated in section in FIG. 8. In FIG. 8,electrically insulating joining portions 25 a are simply those portionsof insulating support structure 31 not overlaid by sheets 23 a.

It is contemplated that electrically conductive sheets 23 may comprisematerials in addition to the electrically conductive polymer. Forexample, a metal may be electrodeposited to the electrically conductivepolymer for increased conductivity. In this regard, the use of adirectly electroplateable resin (DER) may be particularly advantageous.

A further embodiment of fabrication of interconnection substrate unit 22is illustrated in FIGS. 9 and 10. In FIG. 9, electrically conductivesheet 23 b comprises electrically conductive polymer impregnated into afabric or web 32. A number of known techniques can be used to achievesuch impregnation. Insulating joining portion 25 b in FIG. 9 is simplyan un-impregnated extension of the web 32. Fabric or web 32 can beselected from a number of woven or non-woven fabrics, includingnon-polymeric materials such as fiberglass.

Referring now to FIG. 11, an alternate embodiment for the substratestructures of the present invention is illustrated. In the FIG. 11, asupport web or film 33 extends among and supports multiple individualcell units, generally designated by repeat dimension 34. Electricallyconductive sheets 35 are analogous to sheet 23 of FIGS. 6 through 10. Atthe stage of overall manufacture illustrated in FIG. 11, electricallyconductive sheets 35 need not comprise an electrically conductivepolymer as do sheets 23 of FIGS. 6 through 10. However, as will beshown, electrically conducting means, typically in the form of anelectrically conductive polymer containing adhesive, must eventually beutilized to join photovoltaic laminate 10 to the top surface 50 ofelectrically conductive sheets 35. In addition, the electricallyconducting sheets 35 must be attached to the support carrier 33 withintegrity required to maintain positioning and dimensional control. Thisis normally accomplished with an adhesive, indicated by layer 36 of FIG.12.

Conductive sheets 35 are shown in FIGS. 11 and 12 as having length Y-35,width X-35 and thickness Z-35. It is contemplated that length Y-35 isconsiderably greater than width X-35 and length Y-35 can generally bedescribed as “continuous” or being able to be processed in roll-to-rollfashion. Width X-35 defines a first terminal edge 53 and second terminaledge 54 of sheet 35.

It is important to note that the thickness of the conductive sheets 35,Z-35 must be sufficient to allow for continuous lamination to thesupport web 33. Typically when using metal based foils for sheets 35,thickness between 0.001 cm and 0.025 cm would be chosen.

As with the substrate structures of FIGS. 6 through 10, it is helpful tocharacterize top surface 50 of conductive sheets 35 as having a topcollector surface 51 and a top contact surface 52 separated by animaginary barrier 49. Conductive sheet 35 also is characterized ashaving a bottom surface 80.

Referring now to FIGS. 13A and 13B, a process is shown for laminatingthe metal-based foil supported thin film photovoltaic structure of FIGS.1 through 3 to the substrate structures taught in FIGS. 6 through 12. InFIGS. 13A and 13B, photovoltaic cell structures as illustrated in FIGS.1 through 3 are indicated by numeral 10. Substrate structures as taughtin the FIGS. 6 through 12 are indicated by the numeral 22. Numeral 42indicates a film of electrically conductive adhesive intended to joinelectrically conductive metal-based foil 12 of FIGS. 1 through 3 toelectrically conductive sheet 23 of FIGS. 6 through 10 or electricallyconductive sheets 35 of FIGS. 11 and 12. It will be appreciated by thoseskilled in the art that the adhesive strip 42 shown in FIGS. 13A and 13Bis one of but a number of appropriate metal joining techniques whichwould maintain required ohmic communication. For example, it iscontemplated that methods such as doctor blading a conductive resinprior to lamination, spot welding, soldering, joining with low melttemperature metals or alloys, or crimped mechanical contacts would serveas equivalent methods to accomplish the ohmic joining illustrated asachieved in FIGS. 13 a and 13 b with a strip of conductive adhesive.These equivalent methods can be generically referred to as conductivejoining means. In FIG. 13B, the process of FIG. 13A is illustrated usingthe substrate structure of FIGS. 6 and 7.

Referring now to FIGS. 14 and 15, there is shown the result of thelamination process of FIG. 13 using the substrate structure of FIGS. 6through 10. In these and most subsequent figures, cells 10 are shown asa single layer for simplicity, but it is understood that in thesefigures cells 10 would have a structure similar to that shown in detailin FIG. 2. FIGS. 14A and 15A correspond to the substrate structures ofFIGS. 6 and 7. FIGS. 14B and 15B correspond to the substrate structureof FIG. 8. FIGS. 14C and 15C correspond to the substrate structures ofFIGS. 9 and 10.

In the FIGS. 15A, 15B and 15C, electrically conductive adhesive layer 42is shown as extending completely and contacting the entirety of thesecond surface 66 of metal-based foil supported photovoltaic cells 10.This complete surface coverage is not a requirement however, in thatfoil 12 is highly conductive and able to distribute current over theexpansive width X-10 with minimal resistance losses. For example, thestructure of FIG. 22 shows an embodiment wherein electricalcommunication is achieved between conductive sheet 23 of FIGS. 6 and 7and second surface 66 of foil 12 through a narrow bead of conductivejoining means 61. An additional bead of adhesive shown in FIG. 22 by 44,may be used to ensure spacial positioning and dimensional support forthis form of structure. Adhesive 44 need not be electrically conductive.

In the FIGS. 15A, 15B and 15C, the conductive sheets 23, 23 a and 23 bare shown to be slightly greater in width X-23 than the width of foilX-10. As is shown in FIG. 23, this is not a requirement for satisfactorycompletion of the series connected arrays. FIG. 23 is a sectional viewof a form of the substrate structures of FIGS. 6 and 7 laminated by theprocess of FIG. 13 to the photovoltaic structures of FIGS. 1-3. In FIG.23, width X-10 is greater than width X-23. Electrical communication isachieved through conductive joining means 42 and additional joiningmeans 44 to achieve dimensional stability may be employed. The onlyrequirement of the current invention is that first conductive sheetterminal edge 29 be offset from first photovoltaic cell terminal edge 45to expose a portion of top surface 26 of conductive sheet 23.

In FIG. 23, insulating joining portion 25 is shown as extendingcontinuously from second terminal edge 30 of one conductive sheet 23 tothe first terminal edge 29 of an adjacent conductive sheet. As shown inFIG. 26, this is not necessary. In FIG. 26, metal foil supportedphotovoltaic cell 10 is attached to a first conductive sheet 23 throughelectrically conductive joining means 42 and also to insulating joiningportion 25 of an adjacent substrate structure through adhesive 44. Thus,the substrate structure 22 can be discrete. In the embodiment of FIG.26, the foil based photovoltaic structure 10 is of sufficient strengthto maintain proper spacial relationships and positioning among cells.

Referring now to FIGS. 16 and 17, there is shown an alternate structureresulting from the laminating process of FIG. 13 as applied to thephotovoltaic cells of FIGS. 1-3 and the substrate structure of FIGS. 11and 12. In a fashion similar to that of FIGS. 15, 22, and 23, the firstterminal edge 53 of conductive sheets 35 supported by insulatingsubstrate 33 are slightly offset from the first terminal edge 45 ofphotovoltaic cells 10. This offset exposes a portion of top surface 50of conductive sheet 35. Electrical and mechanical joining of sheets 35with second surface 66 of metal-based foil 12 is shown in FIG. 17 asbeing achieved with conductive adhesive 42 as in previous embodiments.However, it is contemplated as in previous embodiments that thiselectrical and mechanical joining can be accomplished by alternate meanssuch as soldering, joining with compatible low melting point alloys,spot welding, or mechanical crimping.

In FIG. 17, support web or film 33 is shown as extending continuouslyamong many cells. However, it should be clear that support film 33 canbe discontinuous. Support film 33 need only be attached to a portion ofa first sheet 35 and a portion of a second sheet 35 of an adjacent cell.This arrangement would suffice to achieve the desired spacialpositioning among cells and leave exposed a portion of back surface 80of electrically conductive sheet 35.

Comparing the sectional views of FIGS. 15, 22, 23 and 17, one observesmany similarities. The most important common structural similarity isthat the first terminal edges 29 of conductive sheets 23 be offsetslightly from first terminal edge 45 of photovoltaic cells 10 (FIGS. 15,22, 23). Similarly, first terminal edges 53 of conductive sheets 35 areslightly offset from first terminal edges 45 of photovoltaic cells 10(FIG. 17). As will be shown, the resulting exposed top surface portionsare used as contact surfaces for the final interconnected array.

It should also be observed that the structures equivalent to those shownin FIGS. 16 and 17 can also be achieved by first joining photovoltaiccells 10 and conductive sheets 35 with suitable electrically conductivejoining means 42 to give the structure shown in FIG. 24 and laminatingthese strips to an insulating support web 33. An example of such anequivalent structure is shown in FIG. 25, wherein the laminates of FIG.24 have been adhered to insulating web 33 in defined repeat positionswith adhesive means 57 and 44. As mentioned above and as shown in FIGS.24 and 25, conductive sheets 35 do not have to contact the whole of thebottom surface 66 of photovoltaic cell 10. In addition, support web 33need not be continuous among all the cells. The support web 33 need onlyextend from the adhesive means 57 of one cell to the adhesive attachment44 of an adjacent cell. This arrangement would leave a portion of thebottom surface 66 of foil 12, and perhaps a portion of the bottomsurface 80 of conductive sheet 35 exposed.

Referring now to FIGS. 18 and 19, insulating beads 56 and 60 ofinsulating material having been applied to the first and second terminaledges 45 and 46 respectively of photovoltaic cells 10. While these beads56 and 60 are shown as applied to the structure of FIG. 15 a, it isunderstood that appropriate beads of insulating material are alsoenvisioned as a subsequent manufacturing step for the structures ofFIGS. 15 b, 15 c, 17, 22, 23, 25, and 26. The purpose of the insulatingbeads is to protect the edge of the photovoltaic cells fromenvironmental and electrical deterioration. In addition, as will beshown the insulating bead allows for electrical interconnections to bemade among adjacent cells without electrical shorting.

It is noted that the application of insulating material 56 to firstterminal edge 45 of photovoltaic cells 10 effectively divides the topsurfaces 26 and 50 of conductive sheets 23 and 35 respectively into tworegions. The first region (region 48 of surface 26 or region 52 ofsurface 50) can be considered as a contact region for seriesinterconnects among adjacent cells. The second region (region 47 ofsurface 26 or region 51 of surface 50) can be considered as the contactregion for interconnecting the substrate to the second surface 66 ofphotovoltaic cells 10.

Referring now to FIGS. 20 and 21, there is shown the method of formingthe final interconnected array. Grid fingers 58 of a highly electricallyconductive material are deposited to achieve electrical communicationbetween the top surface 59 of the photovoltaic cell 10 and the remainingexposed contact regions 48 or 52 of an adjacent cell. It is contemplatedthat these fingers can be deposited by any of a number of processes todeposit metal containing or metal-based foils or films, including maskedvacuum deposition, printing of conductive inks, electrodeposition orcombinations thereof. In the embodiments of FIGS. 20 and 21, the netcurrent flow among cells will be understood by those skilled in the artto be in the direction of the double pointed arrow labeled “I” in thefigures.

Referring now to FIG. 27, the starting material for yet anotherembodiment is illustrated in plan view. Web, mesh or fabric strip 90 ischaracterized by having a width “W” and a length “L”. It is contemplatedthat length “L” is considerably greater than width “W” and length “L”can generally be described as “continuous” or being able to be processedin a roll-to-roll fashion. FIG. 28, a greatly magnified plan view of aportion of the structure of FIG. 27, shows the fabric 90 comprisingfibrils 92 interwoven to form a sturdy structure. Holes 94 are presentamong the interwoven fibrils. It is understood that the fibrils need notbe actually interwoven as shown. Equivalent structures comprisingfibrils and holes, such as polymeric non-woven fabric or adhesivelybonded fibril mats, can be employed.

FIGS. 29 and 30 are sectional views of the embodiment of FIG. 28 takensubstantially along line 29-29 and line 30-30 of FIG. 28 respectively.

FIG. 31 is a greatly simplified sectional representation of thestructure depicted in FIGS. 29 and 30. This simplified representation ofFIG. 31 is useful in the illustration of subsequent embodiments.

Referring now to FIG. 32, there is shown the material shown in FIG. 27following an additional processing step. The material of width “W” isnow generally designated as 104 to indicate this additional processstep. Width “W” has been further defined as comprising three minorwidths “W1”, “W2”, and “W3”. Each of these widths “W1”, “W2”, and “W3”is understood to extend along length “L” as indicated.

FIG. 33 is a greatly magnified plan view of the portion of FIG. 32structure identified as minor width “W2”. In contrast to the plan viewshown in FIG. 28, the structure of FIG. 33 appears continuous in thetwo-dimensional plan view. This continuity results from coating thefibrils with an electrically conductive coating. The structure of thecoated fibrils is best shown in the sectional view of FIG. 34, which isa view taken substantially along line 34-34 of FIG. 33. In FIG. 34,fibrils 92 in the region “W2” have been coated with electricallyconductive coating 96. It is anticipated that coating 96 and thedeposition process for applying coating 96 can be chosen from any numberof suitable techniques. Included in such techniques are painting,dipping, or printing of conductive inks, laminating, and masked chemicalor vapor deposition of metals or other conductive materials. In the caseof a temperature resistant fabric such as fiberglass, deposition of alow melting point metal such as solder could be employed. A particularlyadvantageous coating 96 to prepare the structure of FIG. 34 is directlyelectroplateable resin (DER) applied as a ink, paint solution or paste.The DER is inexpensive, and readily formulated and applied from solutionform.

A method to form an equivalent structure to that shown in FIG. 34 wouldbe to manufacture portion “W2” from a woven or non-woven web of solidDER fibrils.

The important feature of the structure of FIG. 34 is that through-holeelectrical communication extends from the top surface 98 to the bottomsurface 100 in the region defined by “W2” of FIG. 34. This situation isreadily achieved by using the coated fabric or solid DER web approachesof the present embodiments.

FIG. 35 is a sectional view similar to FIG. 34 following an additionaloptional process step. In FIG. 35, the electrical conductivity andmechanical and environmental integrity of the structure is furtherenhanced by applying an additional highly conductive coating 102overlaying coating 96. This subsequent coating 102 can be convenientlyapplied by metal electrodeposition. The structure of FIG. 35 giveshighly conductive communication, equivalent to a metal screen, from topsurface 98 to bottom surface 100 in region “W2” by virtue of thethrough-hole electrodeposition.

Referring now to FIG. 36, there is shown a simplified plan view of the104 structure intended to facilitate teaching of the processing stepsenvisioned to accomplish manufacture of the series connectedphotovoltaic arrays using the substrate structure 104. In FIG. 36, theregions “W1” and “W3” have structure shown in detail in FIGS. 28-30. InFIG. 36, region “W2” has structure shown in detail in FIGS. 33 and 34and optionally FIG. 35.

Referring now to FIG. 37 a, there is shown a simplified sectional viewof the 104 structure employing the “W2” structure depicted in FIG. 34.FIG. 37 b shows a similar view of the 104 structure employing the “W2”structure depicted in FIG. 35. These simplifications will helpillustration of the processing steps and the structures resulting fromthese processing steps.

Referring now to FIG. 38 there is shown a schematic depiction of aprocess for joining the foil supported thin film photovoltaic structureof FIGS. 1 through 3 with the substrate strips 104. Photovoltaic cells10 are continuously fed to the process in spaced relationship tosubstrate strips 104. The process accomplishes attaching one edgeportion of cells 10 to a portion “W3” of one substrate strip 104 and anopposite edge portion of cells 10 to a portion “W1” of a secondsubstrate strip 104.

FIGS. 39 and 40 illustrate the process of FIG. 38 in more detail. InFIG. 39, spacially positioned substrate strips 104 are continuously fedto the joining process 110 from roll 106. Spacially positionedphotovoltaic cells 10 are continuously fed to the process 110 from roll108. The resultant combined structure is designated by the numeral 112.

FIG. 40 illustrates the process of FIG. 39 from the perspective of line40-40 of FIG. 39.

FIG. 41 is a plan view of the combined structure resulting from joiningprocess 110.

FIG. 42A is a simplified sectional view taken substantially along line42-42 of FIG. 41 of the product from process 110 when structure 104shown in FIG. 37A is employed. Adhesive bead 114 is used to attach afirst edge portion 118 of photovoltaic cell structure 10 to portion “W3”of a substrate strip and adhesive bead 116 attaches the second edgeportion 120 of cell 10 to portion “W1” of another substrate strip.Insulating beads 56 and 60 protect the first and second terminal edgesof photovoltaic cells 10.

FIG. 42B is a structure similar to 42A but shows that the substratestructure need not be discrete strips but can be joined. This isequivalent to stating the portion “W1” of one strip is joined to portion“W3” of another strip. Maintenance of spacial positioning and mechanicalintegrity are promoted by the structure depicted in FIG. 42B.

FIG. 42C is a view similar to FIG. 42A but employing the substratestructure 104 shown in FIG. 37B.

FIG. 43 is an enlarged view of the structural portion within circle “A”of FIG. 42A.

FIG. 44A is a view similar to FIG. 43 but following an additionalmanufacturing step in preparation of the series connected array. In FIG.44A an electrically conductive coating 122 extends from the top surface59 of photovoltaic cell 10A over insulating bead 60 and to electricallyconductive region “W2”. Coating 122 can comprise a number ofelectrically conductive media, such as conductive inks or conductiveadhesives. Appropriate conductive inks or adhesives can be applied bysilk screening, masked printing, or simple extrusion of moltenconductive thermoplastic. Alternate forms of applying coating 122 arechemical or vacuum deposition of conductive materials in conjunctionwith appropriate masking techniques.

As indicated in FIG. 44A, conductive coating 122 extends outward acrossthe surfaces of cells 10A, 10B in the form of grid fingers. These gridfingers obviously do not cover the entire top surface 59 of cell 10, butare positioned in spaced relationship on the surface. This arrangementis best shown by the plan view of FIG. 44.

FIG. 44A also shows an electrically conductive coating 124 extendingfrom the second lower surface 66 of cell 10B and to electricallyconductive region “W2”. Coating 124 need not be the same composition norapplied by the same process as coating 122.

FIG. 44A shows that electrical communication is established between thetop surface 59 of photovoltaic cell 10A and the bottom surface 66 ofadjacent photovoltaic cell 10B. However, coatings 122 and 124 may notsupply sufficient conductivity, either because coating resistivities arehigh relative to pure metals or coating thicknesses are small, as wouldbe the case with vacuum or chemical deposited metal coatings. Theconductivity of the grid fingers can be further enhanced to minimizeresistive power losses by depositing additional metal or metal-basedmaterial onto fingers 122. In a preferred embodiment, this additionalmetal or metal-based material is applied by electrodeposition. This isaccomplished by first employing masking techniques to cover those areasof top surface 59 not covered by grid coating 122 with a protectiveinsulating coating. The insulating coating prevents electrodeposition onthose areas and also protects the surface from the possible deleteriouseffects of the electroplating solution. Masking techniques well known inthe art are envisioned, and can be as simple a registered pad printingof an insulative organic coating. The plan views of FIG. 44 indicatesthe location of the insulative masking coating 150. The structuredepicted in FIGS. 44 and 44A may be continuously passed through one ormore metal electrodeposition baths to result in the structure depictedin the sectional view of FIG. 45. In FIG. 45, the electrodepositedmaterial 126 extends from the top surface 59 of cell 10A to the bottomsurface 66 of adjacent cell 10B by virtue of the holes in region “W2”.As with other embodiments, the direction of net current flow is shown bythe double pointed arrow labeled “I” in FIG. 45. Those skilled in theart will recognize that a similar combination of conductive coating 122and electrodeposit 126 may be used to produce the grid fingers 58depicted in FIGS. 20 and 21. In the embodiments depicted in FIGS. 20, 21and FIG. 45, the fact that the bottom surfaces 66 (FIG. 45) and 28 (FIG.21) are conductive and exposed facilitate the continuouselectrodeposition step by allowing cathodic contacting to these bottomsurfaces, exposing the opposite top surfaces to the electroplatingbaths.

In a preferred embodiment of the grid structure taught above inconjunction with FIGS. 20, 21 and FIG. 45 conductive grid coating 122comprises a DER. “DERS” are inexpensive, can be formulated to achievegood adhesion and ohmic contact to top surface 59 comprising thetransparent conductive oxide (TCO), and achieves good ohmic contact andadhesion to the electrodeposit 126. In essence, the DER functions as a“conductive adhesive” joining the TCO and the electrodeposit 126. Thoseskilled in the art will recognize that electrodeposit 126, whileillustrated as a single layer, may comprise multiple layers.

FIG. 49 is a sectional view similar to FIG. 43 of an alternativeintermediate article resulting from feeding the material of FIGS. 27through 31 to the process of FIGS. 38 through 40 rather than the joiningstrips 104 of FIGS. 36 and 37. Here the conductive coating 96 definingregion “W2” of FIGS. 36 and 37 has not been applied. However, applyingthe conductive coating 96 to the FIG. 49 structure at the time ofapplying conductive coatings 122 and 124 (see discussion of FIG. 44A),results in converting the FIG. 49 structure into one equivalent to thatshown in FIG. 44A.

FIG. 46 shows yet another embodiment of the current disclosure. The planview of 46 illustrates a polymer based sheet 130 of width “W” subdividedinto three areas “W1”, “W2”, and “W3” in fashion similar to that of FIG.32. Polymer based sheet 130 can be conveniently formed by coextrusion ofmaterials 132, 134, and 136, corresponding to regions “W1”, “W2”, and“W3” respectively. Materials 132, 134, and 136 can be all based on thesame polymer or different polymers can be chosen. It is importanthowever that proper joining integrity be established at matinginterfaces 138 and 140.

The material 134 chosen for region “W2” is an electrically conductivepolymer. A particularly advantageous resin is a DER.

FIG. 47 is a sectional view taken substantially along line 47-47 of FIG.46. As shown in FIGS. 46 and 47, region “W2” is caused to have holes 142along its length. In the simplest conceptual case, these holes aresimply punched in the region “W2”. Another approach would be toformulate the region “W2” of FIGS. 46 and 47 from a fabric (non-woven orwoven) of electrically conductive polymer.

FIG. 48 shows the structure of FIG. 47 following an additionalprocessing step of depositing metal 144 through holes 142 to establishhigh electrical conductivity from top surface 146 to bottom surface 148.Preferably this metal deposition is by electroplating although chemicaland vapor deposition techniques could be used.

In many respects the structures shown in FIGS. 47 and 48 resemble thestructures depicted in FIGS. 37 a and 37 b respectively. Thus the use ofthe structures of FIGS. 47 and 48 in the process of FIGS. 38 through 40would give results similar to those previously taught as one skilled inthe art will recognize.

It is important to recognize that the unique design and process taughtby the present invention is accomplished in a fully additive fashion. Nowasteful and costly material removal steps are needed to achieve theintegrated series connected arrays taught. This is a significantadvantage over the prior art.

Despite the relative simplicity envisioned for production of the currentcollector grid/interconnect structures using the combination “conductivecoating plus electrodeposition” approach taught above in conjunctionwith FIGS. 20, 21 and FIGS. 44, 44A and 45, it can be contemplated thatseparate production of the grid/interconnect array followed bysubsequent application to a geometrically registered arrangement ofphotovoltaic cells may be employed to advantage. This concept wouldavoid the masking and possible exposure of the photovoltaic cells to thewet electrochemistry involved in the approaches taught above inconjunction with FIGS. 20, 21 and 44, 44A and 45. Thus, a furtherembodiment of the grid structure, design and fabrication process istaught below in conjunction with FIGS. 50 through 66.

FIG. 50 is a plan view of a polymeric film or glass substrate 160.Substrate 160 has width X-160 and length Y-160. In one embodiment,taught in detail below, Y-160 is much greater than width X-160, wherebyfilm 160 can generally be described as “continuous” in length and ableto be processed in length Y-160 in a continuous roll-to-roll fashion.FIG. 51 is a sectional view taken substantially from the view 51-51 ofFIG. 50. Thickness dimension Z-160 is small in comparison to dimensionsY-160, X-160 and thus substrate 160 has a sheetlike structure. As shownin FIG. 51, substrate 160 may be a laminate of multiple layers 162, 164,166 etc. or may comprise a single layer of material. The multiple layers162,164,166 etc. may comprise inorganic or organic components such asthermoplastics or silicon containing glass-like layers. The variouslayers are intended to supply functional attributes such asenvironmental barrier protection or adhesive characteristics. Suchfunctional layering is well-known and widely practiced in the plasticpackaging art. Sheetlike substrate 160 has first surface 190 and secondsurface 192.

FIG. 52 depicts the structure 160 (possibly laminate) as a single layerfor purposes of presentation simplicity. Substrate 160 will berepresented as this single layer in the subsequent embodiments.

FIG. 53 is a plan view of the structure following an additionalmanufacturing step, and FIG. 54 is a sectional view taken along line54-54 of FIG. 53.

FIG. 55 is a sectional view taken along line 55-55 of FIG. 53. In FIGS.53 through 55, it is seen that a pattern of “fingers”, designated 170,extends from “buss” structures, designated 171. Both “fingers” 170 and“busses” 171 are deposited on and supported by substrate 160. Whileshown as a single layer, “fingers” 170 and “busses” 171 may comprisemultiple layers. “Fingers” 170 and “busses” 171 may compriseelectrically conductive material, or may comprise non-conductivematerial which would assist accomplishing a subsequent deposition ofconductive material. For example, “fingers” 170 or “busses” 171 couldcomprise a seeded polymer which would catalyze chemical deposition of ametal in a subsequent step. A second example would be materials selectedto promote adhesion of a subsequently applied conductive material.“Fingers” 170 and “busses” 171 may differ in actual composition.

FIGS. 56, 57 and 58 correspond to the views of FIGS. 53, 54 and 55following an additional processing step. FIG. 59 is a sectional viewtaken substantially along line 59-59 of FIG. 56. FIGS. 56 through 59show additional conductive material deposited onto the “fingers” and“busses” of FIGS. 53 through 55. This additional conductive material isdesignated by layers 173,175. While shown as multiple layers 173,175, itis understood that this conductive material could be a single layer. Asbest shown in FIG. 58, “fingers” 170 have top free surface 185 and“busses” 171 have top free surface 187. In a preferred embodiment,additional layers 173,175 etc. are deposited by electrodeposition,taking advantage of the deposition speed, low cost and selectivity ofthe electrodeposition process. Alternatively, these additionalmetal-based layers may be deposited by selective chemical deposition orregistered masked vapor deposition. Metal-filled conductive resins mayalso be used to form these additional layers 173,175.

FIGS. 60 through 63 illustrate a process 177 by which theinterconnection component of FIGS. 56 through 59 is combined with thestructure illustrated in FIG. 19 to accomplish series interconnectionsamong geometrically spaced cells. In FIG. 60 roll 179 represents a“continuous” feed roll of the grid/buss structure on the sheetlikesubstrate as depicted in FIGS. 56 through 59. Roll 181 represents a“continuous” feed roll of the sheetlike geometrical arrangement of cellsdepicted in FIG. 19. As indicated in FIGS. 60 through 63, process 177laminates these two sheetlike structures together in a spacialarrangement wherein the grid “fingers” project laterally across the topsurface 59 of cells 10 and the “finger/buss” structure extends to thetop contact surface 48 of an adjacent cell. As with prior embodiments,the double pointed arrow labeled “i” indicates the direction of netcurrent flow in the embodiments of FIGS. 62 and 63.

The actual interconnection between adjacent cells is depicted in greatlymagnified form in FIG. 63, magnifying the encircled region “A” of FIG.62. In the embodiments of FIGS. 62 and 63, “buss” structure(171,173,175) is shown to extend in the “continuous” Y direction of thelaminated structure (direction normal to the paper). It will beappreciated by those skilled in the art that the only electricalrequirement to achieve proper interconnection of the cells is that thegrid “fingers” extend to the contact surface 48 of an adjacent cell.However, in those cases where the grid fingers comprise anelectrodeposit, inclusion of the “busses” provides a convenient way topass electrical current by providing a continuous path from therectified current source to the individual grid “fingers”. Thisfacilitates the initial electrodeposition of layers 173, 175 etc. ontothe originally deposited materials 170, 171. Those skilled in the artwill recognize that if the grid “fingers” comprise material deposited byselective chemical, masked vapor deposition or printing, the grid“fingers” could constitute individual islands and the “buss” structurecould be eliminated.

Those skilled in the art will recognize that contact between the topsurface 59 of the cell and the mating surface 185 of the grid fingerwill be achieved by ensuring good adhesion between first surface 190 ofsheet 160 and the top surface 59 of the cell in those regions wheresurface 190 is not covered by the grid. However, electrical contactbetween grid “fingers” 170 and cell surface 59 can be further enhancedby selectively printing a conductive adhesive onto “fingers” 170 priorto the lamination process taught in conjunction with FIGS. 60 and 61. Inthis way surface 185 is formed by a conductive adhesive resulting insecure adhesive and electrical joining of grid “fingers” 170 to topsurface 59 following the lamination process.

Alternatively, one may employ a low melting point metal-based materialas a constituent of the material forming surface 185. In this case thelow melting point metal-based material is caused to melt during theprocess 177 of FIG. 60 thereby increasing the contact area between themating surfaces 185 and 59. In a preferred embodiment indium or indiumcontaining alloys are chosen as the low melting point contact materialat surface 185. Indium melts at a low temperature, considerably belowpossible lamination temperatures. In addition, Indium is known to bondto glass and ceramic materials when melted in contact with them. Givensufficient lamination pressures, only a very thin layer of Indium wouldbe required to take advantage of this bonding ability.

Bonding to the contact surface 48 of conductive sheet 23 can beaccomplished by any number of the electrical joining techniquesmentioned above. These include electrically conductive adhesives,solder, and melting of suitable metals or metal-base alloys during theheat and pressure exposure of the process 177 of FIG. 60. As with thediscussion above concerning contact of the “fingers”, selecting lowmelting point metal-based materials as constituents forming surface 187could aid in achieving good ohmic contact and adhesive bonding of“busses” 171 to the contact surface 48 of sheet 23.

FIGS. 64 through 66 show the result of the FIG. 60 process using asubstrate structure similar to that illustrated in FIG. 37B, except thatthe portion “W-3” shown in FIG. 37B is omitted. FIG. 65 showsphotovoltaic cells 10 spacially arranged using the substrate structureof FIG. 64. Conductive joining means 202 connect cells 10 to portions oftop surface 200 of conductive regions W-2. Insulating beads 56,60protect the edges of cells 10. Adhesive 204 attaches cell 10 to thenon-conductive region W-1 of the substrate. The structure depicted inFIG. 65 is similar in electrical and spacial respects to the structuredepicted in FIG. 19. Substituting the structure of FIG. 65 for the FIG.19 structure shown in the prior embodiments of FIGS. 60 through 63results in the structure shown in the sectional view of FIG. 66. In thiscase the through-holes associated with the FIG. 64 substrate structuresmay assist in the lamination process by permitting a reduced pressure onthe bottom side 206 of the sheetlike structures (FIG. 65) therebypromoting removal of air from between the sheetlike structures of FIGS.56 through 59 and the sheetlike structure of FIG. 65 just prior tolamination.

The sectional views of FIGS. 63 and 66 embody application of theinvention to the substrate structures taught in FIGS. 7 and 64respectively. It is understood that similar results would be achievedusing the other substrate structures taught in the disclosure, such asthose embodied in FIGS. 8 through 12, 24 and 25, 26, 27 through 37B, 46through 48, and 49.

The sectional view of FIGS. 63 and 66 show film 160 remaining as part ofthe structure following the process 177 of FIG. 60. In some cases in maybe advantageous to employ film 160 in a manner wherein it is removedafter attachment of the “fingers” and “busses” to the respectivesurfaces of the cells and substrate. In this application, the film 160would serve as surrogate support and spacial positioning means duringformation, placement and bonding of the “finger/buss” structure. In thiscase a suitable “release” material would be positioned between surface190 of film 160 and “fingers/busses” 170/171.

A further embodiment of a front face current collector structure istaught in conjunction with FIGS. 67 through 81. FIG. 67 is a top planview of a metal foil/semiconductor photovoltaic structure similar to thelaminated structure depicted in FIGS. 1 and 2. However, the structure ofFIG. 67, generally referred to as 300, also includes narrow strips ofinsulating material 302 extending in the length direction Y-300. Strips302 are usually positioned at repeat distances R in the width directionX-300 of structure 300. As will be seen below, dimension R approximatesthe width X-10 of the eventual individual cells.

FIG. 68 is a sectional view taken substantially along line 68-68 of FIG.67. FIG. 68 shows a laminate comprising separate layers 75,13,14,11, and18 as previously described for the structure of FIG. 2. Insulatingstrips 302 are shown positioned on top surface 59 of structure 300.However, it is understood that strips 302 could be positioned on topsurface 303 of semiconductor material 11. In this latter case, windowelectrode 18 could be deposited over the entire surface (includingstrips 302) or selectively onto the surface areas between strips 302.For simplicity, the embodiments of FIGS. 67 through 78 will show strips302 disposed on top surface 59 of window electrode 18. The purpose ofthe insulating strips 302 is to prevent shorting between top and bottomelectrode material during subsequent slitting into individual cells, aswill become clear below.

In the embodiment shown, length Y-300 is much greater than width X-300and length Y-300 can generally be described as “continuous” or beingable to be processed in roll-to-roll fashion. In contrast to width X-10of the individual cell structure of FIGS. 1 and 2, X-300 of FIGS. 67 and68 is envisioned to be of magnitude equivalent to the cumulative widthsof multiple cell structures. Strips 302 are typically 0.002 inch to0.050 inch wide (dimension “T”, FIG. 67). Strips 302 can be applied tothe surface 59 by any number of methods such as thermoplastic extrusion,roll printing or photo masking.

In order to promote simplicity of presentation, layers 75,13,14,11 and18 of structure 300 will be depicted as a single layer 370 in subsequentembodiments.

FIG. 69 is a top plan view of the FIG. 67 structure following anadditional processing step and FIG. 70 is a sectional view takensubstantially along line 70-70 of FIG. 69. Electrically conductivematerial has been deposited in conductive strips 304 onto the topsurface of the structure 300. Strips 304 extend in the width directionX-300 and traverse a plurality of repeat distances “R”. Dimension “N” ofstrips 304 is normally made as small as possible, typically 0.002 inchto 0.100 inch. Dimension “C”, the repeat distance between strips 304depends to some extent on dimension “N” but is typically 0.05 inch to1.0 inch.

Strips 304 can comprise electrically conductive resins or adhesivesapplied by printing or thermoplastic extrusion. Alternatively, strips304 can comprise metal-based materials applied by selective deposition.It is, of course, advantageous to select materials and techniques whichpromote adhesive and ohmic contact to the top surface 59 of windowelectrode 18. As will be appreciated by those skilled in the art inlight of the following teachings, electrically conductive resins, andDER's in particular, are very suitable as materials for conductivestrips 304.

In the embodiment of FIG. 69, those areas of the top surface ofstructure 300 not covered with conductive strips 304 have been coatedwith a thin coating of electrically insulating material 305.

FIG. 71 is a plan view of an alternate embodiment. In FIG. 71, 300Adesignates a structure similar to the structure 300 of FIGS. 67, 68 butstrips 302 are not shown. They have either been excluded or areinvisible in the plan view of FIG. 71, having been deposited on thesurface of semiconductor material 11 (and thus overcoated with windowelectrode 18) or covered by insulating layer 305A. 304A designatesstrips or islands of electrically conductive material which havedimension “Q” slightly less than repeat distance “R”. Those skilled inthe art will recognize, in light of the teachings that follow below,that the structure embodied in FIG. 71 would be conceptually equivalentto the structure of FIG. 69.

FIG. 72 is a sectional view similar to FIG. 70 after an additionalprocessing step. In FIG. 72, additional highly electrically conductivematerial 306 has been deposited overlaying conductive material 304.Material 306 has exposed top surface 352. In a preferred embodiment,highly electrically conductive material 306 is electrodeposited.Electrodeposition permits relatively rapid deposition rates and permitsfacile deposition of very conductive materials such as copper andsilver. In this regard, it is highly advantageous to employ a DER forthe conductive material 304. It can be appreciated that material strips304/306 extend in the “X” direction a distance equivalent to multiplewidths “R”. This concept therefore allows for deposition of theindividual cell grid fingers in an essentially continuous, “bulk”fashion.

FIG. 73 is a sectional view of a portion of the FIG. 72 structure afteran additional processing step comprising slitting the FIG. 72 structurealong the insulating strips 302 at repeat distances “R” to giveindividual units 308 comprising laminate portions of structures 370,302, 304, 306 of the prior embodiments. Units 308 have width “R” which,as will be seen, approximates the eventual photovoltaic cell width.During this slitting process, insulating beads 302 prevent smearing ofthe top conductive material to the bottom electrode material 12 whichwould result in electrical shorting.

FIG. 74 is a view similar to FIG. 13B showing the FIG. 73 structuresjust prior to a laminating process similar to FIG. 13A. Individualstructures 308 are positioned in spacial relationship with electricallyconductive adhesive 42 and conductive sheets 23. As in priorembodiments, sheets 23 are separated by insulating joining portions 25.Conductive sheets 23 can be considered to have a top contact surfaceregion 48 and top collector surface area 47.

FIG. 75 is a sectional view of the structure after the laminationdepicted in FIG. 74 plus an additional step of applying insulating beads56,60 to the terminal edges of the individual units 308. As shown inFIG. 75, at least a portion of top contact surface 48 remains exposedfollowing this lamination. In addition, the lamination is characterizedby repeat dimension 34, which is slightly greater than dimension

FIG. 76 is a sectional view prior to a further laminating step in theproduction of the overall array. FIG. 76 shows introduction of anadditional sheetlike interconnection component 309 comprising materialstrips 316 mounted on sheet 310 having top surface 312 and bottomsurface 314. Sheet 310, shown as a single layer for simplicity, maycomprise a laminate of multiple layers of materials to supply adhesiveand barrier properties to the sheet.

Mounted in spaced arrangement on the bottom surface 314 of sheet 310 arestrips 316 of material having an exposed surface 340 which iselectrically conductive. Strips 316 are also shown in FIG. 76 tocomprise layer 320 which adhesively bonds conductive layer 318 to sheet310. Layer 320 need not necessarily be electrically conductive and maybe omitted if adhesion between conductive material 318 and sheet 310 issufficient. Layer 18 may comprise, for example, an electricallyconductive adhesive.

FIG. 77, a plan view taken substantially along line 77-77 of FIG. 76,indicates the linear nature of strips 316 extending in the directionY-309. Strips 316 have a width dimension “B” sufficient to span thedistance between conductive strips 306 of one unit 308 to the contactsurface 48 of sheet 23 corresponding to an adjacent unit. Typicalmagnitudes for dimension “B” are from 0.020 inch to 0.125 inch dependingon registration accuracy during the multiple lamination processesenvisioned.

FIGS. 78 and 79 present alternatives to the FIG. 77 component. In FIG.78, tab extensions 322 of width “E” reach out in the “X” direction fromthe strips 316A. Tabs 322 are positioned at repeat distances “C” in the“Y” direction corresponding to the repeat dimension “C” of theconductive strips 304/306. Proper positional registration during thelamination process envisioned in FIG. 76 allows tabs 322 to overlap andcontact strips 306, permitting increased contact area between strips 306and tabs 322 and also a possible reduction in width “D” of strips 316 a(FIG. 78) in comparison to dimension “B” (FIG. 77).

FIG. 79 shows an alternate embodiment wherein strips 316 and 316A ofFIGS. 77 and 78 respectively have been replaced by individual islands316B. Thus, material forming conductive surface 340 need not becontinuous in the “Y” direction. Islands 316B can comprise, for example,an electrically conductive adhesive. Dimension “E” (FIG. 79) is similarto dimension “N” (FIG. 69). Dimension “D”, (FIG. 79) is sufficient tospan the distance between conductive strips 306 of one unit 308 to thecontact surface 48 of sheet 23 corresponding to an adjacent unit.

Since the linear distance between strips 306 of one unit 308 and surface48 corresponding to an adjacent unit is small, the structures 316, 316 aand 322, and 316 b of FIGS. 77, 78, and 79 respectively do notnecessarily comprise materials exhibiting electrical conductivitiescharacteristic of pure metals and alloys. However, as will be discussedbelow, proper selection of metal-based materials to form surface 340 ofthese structures can be used to advantage in achieving excellent ohmicand adhesive contacts to grid material 306 and contact surfaces 48 ofconductive sheets 23.

Accordingly, an example of a laminated structure envisioned forconductive layer 318 is shown in the sectional view of FIG. 80. A layerof electroplateable resin 324 is attached to adhesive layer 320 (layer320 not shown in FIG. 80). This is followed by layers 326,328 ofelectrodeposited metal for mechanical and electrical robustness. Finallya layer of low melting point metal or alloy 330 is deposited to producefree surface 340. Those skilled in the art will recognize that DER'swould be a highly attractive choice for resin layer 324. Alternatively,a material, not necessarily conductive, which would allow selectivedeposition of metal by chemical techniques could be chosen for layer324.

Using the structure embodied in FIG. 80 for the layer 318, the material330 with surface 340 is caused to melt during the lamination processdepicted in FIG. 76, resulting in a “solder” bond between materialforming contact surface 48 of sheet 23 and material 330 with surface340. A similar “solder” bond is formed between material forming topsurface 352 of strip 306 and material 330 having surface 340.

One will note that the retention of sheets 310 of FIGS. 76 through 78 isnot an absolute requirement for achieving the electricalinterconnections among cells, but does facilitate handling andmaintenance of spacial positioning during formation of the conductiveinterconnect structures and the subsequent laminating process envisionedin FIG. 76. In this regard, sheet 310 could be a surrogate support whichis removed subsequent to or during lamination. This removal could beachieved, for example, by having layer 320 melt during the laminationprocess to release sheet 310 from structure 316, etc.

One also should recognize that the electrical interconnections betweengrid material 306 of units 308 and contact surface 48 corresponding toan adjacent cell could be made by using individual “dollops” ofconductive material spanning the gap between surface 48 and eachindividual grid finger of an adjacent cell.

FIG. 81 is a greatly exploded view of a completed interconnectionachieved according to the teachings embodied in FIGS. 67 through 80.FIG. 81 shows first cell 360 and a portion of adjacent cell 362.Interconnect region 364 is positioned between cells 360 and 362. It isseen that robust, highly efficient top surface current collection andcell interconnections are achieved with inexpensive, controllable andrepetitive manufacturing techniques. Sensitive, fine processinginvolving material removal techniques and adversely affecting yields areavoided. The double pointed arrow “i” in FIG. 81 indicates the directionof net current flow among the interconnected cells.

While the grid/interconnect structure taught in conjunction with FIGS.67 through 81 employed the substrate structure depicted in FIGS. 6 and7, it is understood that similar results would be achieved with theother substrate embodiments revealed in conjunction with the teachingscorresponding to FIGS. 8 through 66.

Since the layer 370 exhibits reasonable “through conductivity”, it iscontemplated that the required electrodeposition current could beachieved by contacting the exposed back metallic surface 66 ofmetal-based foil 12. However, it is understood that should thiselectrodeposition current have a deleterious effect on the cell itself,electrodeposition could still be accomplished by masking surface 66 andincluding a “buss” structure of conductive material extending in the“Y-300” direction of the structure shown in FIG. 69.

A further embodiment of the series connected photovoltaic arrays of theinstant disclosure is taught in conjunction with FIGS. 82 and 83. FIG.82 is a depiction similar to FIG. 74 illustrating a laminating processresulting in a series interconnected array of multiple photovoltaiccells. FIG. 82 shows multiple cells 308 (as described in conjunctionwith FIG. 73) whose bottom conductive metal-based surface 66 slightlyoverlaps top, light-incident surface 352 of the grid fingers of anadjacent cell. Conductive adhesive strips 42 are positioned in this areaof overlap. Adhesive strips 44 augment positioning and handlingreliability by firmly attaching the cells to support web 400. Should theconductive adhesive bonding imparted by adhesive strips 42 be ofsufficient strength and integrity, support web 400 can be consideredoptional. In addition, conductive adhesive strips 42 are but one ofseveral ways to achieve the electrical joining required, as has beenpreviously disclosed.

FIG. 83 embodies the result of the laminating process of FIG. 82. Theindividual cells 308 are electrically connected in series through a“shingling” arrangement, wherein the bottom conductive surface 66 of afirst cell is electrically and adhesively joined to a light incident topsurface 352 of the current collector grid fingers of an adjacent cell.Insulating strips 60 protect terminal edges of individual cells fromelectrical shorting. The double pointed arrow “I” indicates thedirection of net current flow among cells of the FIG. 83 embodiment.

The simplified series interconnections among multiple photovoltaic cellstaught in the present disclosure are made possible in large measure bythe ability to selectively electrodeposit highly conductive metal-basedmaterials to manufacture both supporting interconnect substrates andcurrent collector grid structures. This selectivity is readily andinexpensively achieved by employing directly electroplateable resins(DERs) as defined herein.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications,alternatives and equivalents may be included without departing from thespirit and scope of the inventions, as those skilled in the art willreadily understand. Such modifications, alternatives and equivalents areconsidered to be within the purview and scope of the invention andappended claims.

1. A device comprising a first photovoltaic cell and a current collectorstructure, wherein, said photovoltaic cell comprises a cell body whichincludes semiconductor material and a light incident top surface portionformed by a transparent or translucent conductive material, said currentcollector structure comprises: a. an optically transparent ortranslucent sheetlike substrate having first and second substratesurfaces, said first substrate surface facing in a direction oppositeand away from said second substrate surface, b. a pattern comprisingmultiple traces separated by regions of said substrate, said tracesextending over said first substrate surface, said traces comprisingmultiple layers wherein, a first of said layers comprises polymericmaterial and has structure in the form of at least a portion of saidpattern, a second of said layers comprises electrically conductivematerial, and wherein said device comprises a combination of saidphotovoltaic cell and said current collector structure such that atleast a portion of said pattern is distributed over a preponderance ofsaid light incident top surface portion, said combination furthercharacterized by having said pattern portion and said light incident topsurface portion facing toward each other such that said second layerassociated with said pattern portion is positioned between the firstlayer and said light incident surface.
 2. The device of claim 1 whereinsaid transparent or translucent conductive material is comprises a metaloxide.
 3. The device of claim 1 wherein said photovoltaic cell ischaracterized as a thin film photovoltaic structure.
 4. The device ofclaim 1 wherein said semiconductor material is disposed over a selfsupporting metal based foil.
 5. The device of claim 1 wherein saidsubstrate includes a layer comprising silicon.
 6. The device of claim 1wherein said first layer is in direct contact with said first substratesurface.
 7. The device of claim 1 wherein said first layer is not indirect contact with said first substrate surface.
 8. The device of claim1 wherein said first and second layers are in direct contact.
 9. Thedevice of claim 1 wherein said first and second layers are not in directcontact.
 10. The device of claim 1 wherein said first layer is a printedstructure.
 11. The device of claim 1 wherein said first layer comprisesa material having the ability to assist in the formation of said secondlayer.
 12. The device of claim 1 wherein said first layer comprises anelectrically conductive filler in a polymeric matrix.
 13. The device ofclaim 1 wherein said first layer comprises a material capable ofinitiating chemical metal deposition.
 14. The device of claim 1 whereinsaid second layer comprises electrodeposited metal.
 15. The device ofclaim 1 wherein said second layer comprises copper.
 16. The device ofclaim 1 wherein said second layer comprises indium.
 17. The device ofclaim 1 wherein a portion of said first substrate surface is adhesivelybonded to said top surface.
 18. The device of claim 1 wherein saidpattern further comprises a buss joining two or more of said multipletraces, and wherein a monolithic material forms portions of both saidbuss and said two or more traces.
 19. The device of claim 18 whereinsaid monolithic material comprises an electrodeposit.
 20. The device ofclaim 18 wherein said photovoltaic cell has terminal edges defined bythe boundaries of said semiconductor material and a portion of said bussis positioned outside a terminal edge of said cell.
 21. A devicecomprising a first photovoltaic cell and a current collector structurewherein, said photovoltaic cell comprises a cell body which includessemiconductor material and a light incident top cell surface formed by atransparent or translucent conductive material and said currentcollector structure comprises: a. a sheetlike substrate, b. a pattern ofmultiple electrically conductive traces extending over a transparent ortranslucent portion of said sheetlike substrate, c. a strip forming abuss in electrical communication with a multiple of said traces, saidbuss comprising multiple layers wherein, a first of said layerscomprises polymeric material and has first and second surface portionsfacing oppositely and away from each other, said first surface portionserving to define a dimension of a second of said layers, said secondlayer comprises metal coating said first surface portion, said secondsurface being devoid of metal coating, said device characterized ashaving at least a portion of said pattern of multiple traces distributedover a preponderance of said light incident top cell surface.
 22. Adevice comprising two photovoltaic cells, said cells having a lightincident top surface and a conductive bottom surface, said cells beingelectrically connected in series through an interconnecting structureconveying current from the top surface of a first cell to the bottomsurface of an adjacent cell, said interconnecting structure comprisingan electrically conductive mesh or fabric, said mesh or fabric havingstructure including, a core structure of polymer based fibrils a metalor metal alloy coating said fibrils.